Field
The invention is directed to a roll of glass as well as a method and apparatus for rolling the glass. More particularly, the invention is directed to a roll of glass ribbon wound together with an interleaf material, as well as to an apparatus and method for rolling them together.
Technical Background
Although formed as a continuous ribbon, glass is typically segmented into sheets as soon as it has cooled and solidified. Recent product trends—in ePaper front plane substrates, protective cover sheets in photovoltaic modules, touch sensors, solid state lighting, and electronics, for example—have resulted in requirements for thinner and thinner glass. As glass thicknesses continue to decrease, however, these sheets become more flexible. This creates a challenge from a handling perspective, particularly for glass of 0.3 mm or thinner. Accordingly, there have been attempts to wind thin glass into a roll as a manner of facilitating handling. However, there are several unique features of glass that create challenges for successfully implementing a winding process.
First the edge “beads” of the glass, as formed, are substantially thicker than the constant thickness area in between. Second, glass is extremely sensitive to surface defects. These defects create stress points that generate cracks and lead to breakage. Thus it is not advisable to have direct surface to surface contact of glass to itself, as is typical in a spooled roll of material. The challenges from these first two characteristics have been addressed by using various interleaf materials between layers of the glass ribbon when winding.
Third, as noticed by the inventors of the subject matter in the present disclosure, and which has gone unaddressed—in terms of effect on winding thin glass ribbon, i.e. 0.3 mm or thinner—is that the forming process can introduce differential thickness across the width of the glass ribbon and/or camber (continuous curvature in one direction caused by, for example, differential cooling between the two edge beads). When winding a glass ribbon with differential cross-ribbon thickness and/or camber, lateral forces are generated in the wound roll that result in angled, rather than straight, side walls on the wound roll. In some cases, the angle of the side wall may lead to the glass ribbon contacting a flange of a spool onto which the glass ribbon is being wound, thereby risking damage to the glass ribbon. Additionally, the angled side wall of the roll leads to difficulties in processing, when unwinding the roll to use the glass ribbon in a continuous manufacturing process. Accordingly, there is a need for methods of, and apparatuses for, winding glass ribbon together with interleaf material so that the roll has straighter side walls.
Fourth, as again noticed by the inventors of the subject matter in the present disclosure, there is then a need to maintain the sidewalls in a straight manner during handling, shipping, and storage of the rolls.